If for some reason you need to reinstall Windows, Office, or other Microsoft applications, and you can’t find the original key on a CD, you’ll be out of luck. You won’t be able to re-install. That is, you won’t unless you use ProduKey.
ProduKey is a little, but useful utility which displays the ProductID and the CD-Key of MS-Office, Windows, and SQL Server installed on your computer.
You can view this information for your current running operating system, or for another operating system/computer – by using command-line options.
This utility can be useful if you lost the product key of your Windows/Office, and you want to reinstall it on your computer.